This invention relates to an air conditioner, and more specifically to a technique for changing a ratio between latent heat and sensible heat in an indoor heat exchanger during running of a cooling cycle, thereby improving capability of dehumidification (latent heat).
An air conditioner in a cooling/heating system has a freezing cycle including a compressor, a four-way valve, an outdoor heat exchanger, an expansion valve and an indoor heat exchanger. During a heating operation, the air conditioner circulates coolant in the course of the compressor→four-way valve→indoor heat exchanger→expansion valve→outdoor heat exchanger→four-way valve→compressor and employs the indoor heat exchanger as a condenser and the outdoor heat exchanger as an evaporator.
On the other hand, during a cooling operation inclusive of dehumidification, the air conditioner circulates the coolant in the course of compressor→four-way valve→outdoor heat exchanger→expansion valve→indoor heat exchanger→four-way valve→compressor, and employs the indoor heat exchanger as the evaporator and the outdoor heat exchanger as the condenser. During the humidification, weak running of the cooling running (“simple cooling operation”) is executed. Meanwhile, during this cooling/dehumidification operation, if the temperature of the indoor heat exchanger has not reached a dew point temperature, the room temperature only falls and the indoor relative humidity rises. So, an unpleasant feeling may be given to users.
Specifically, since the changing rate of latent heat is low as compared with the changing rate of sensible heat by the indoor heat exchanger, the sensible heat is exhibited alone so that owing to the resultant reduction in the room temperature, the relative humidity rises to nearly 100%. Thus, a chilling sense will be given to the users. In recent years, for the purpose of energy saving, an increase in the quantity of wind has been intended. However, with an increase in the quantity of wind, the temperature in the indoor heat exchanger rises and the capability of dehumidification is sacrificed.
In order that the chilling sense is not given to the users during the cooling/dehumidification operation, a proposal of rising the temperature of the air discharged from an indoor unit is described in e.g. Patent Reference 1. In the invention described in Patent Reference 1, a part of the indoor air sucked into an indoor unit is passed through the indoor heat exchanger to create a cold wind at 12 to 15° C. On the other hand, the remaining air is caused to bypass the indoor heat exchanger and is mixed with the cold wind cooled to 12 to 15° C. by the indoor heat exchanger in a mixing chamber in front of the air outlet. The mixed wind is discharged from the air outlet.
Patent Reference 1: JP-A-2000-88327
In accordance with the invention described in Patent Reference 1, the temperature of the discharged air can be set at 20 to 25° C. which does not give a sense of the cold wind. However, in the invention in Patent Reference 1, there are not disclosed a technique for increasing the quantity of dehumidification when a damper is opened/closed for bypassing the indoor heat exchanger, timings of opening the damper, a countermeasure when the damper has caused a failure and a technique for preventing condensation in the indoor blower.